[unreadable] Radiation sources are used throughout our society. By law, each radiation source must be properly shielded. Presently, design of shielded facilities or assemblies is performed via extensive and laborious hand calculations and with simple analytical tools that make use of broad simplifying assumptions. This application proposes the development of a simple, easy-to-use software package for shielded facility design and effective dose determination. Such a package will allow the user to evaluate a range of different shielding scenarios in which materials and/or layout are iteratively altered. This capability is prohibitively laborious and tedious with existing hand calculation approaches. The proposed software package will reside as a thin client on the user's desktop and will consist of an easy-to-use interface into which all details regarding the facility, radiation source, and personnel locations are entered by the user. These inputs will be sent via the Internet to the BioMed Software Inc. server where the software will interpret all entries and assemble an appropriate input file to be run with the MCNP Monte Carlo code. Use of the MCNP code as the simulation engine allows full 3D modeling of the realistic scenario, including many radiation types, creation of secondary particles and full accounting for all interaction process, something not possible with existing approaches. In addition, users will be able to calculate effective dose equivalent, also not possible with the hand calculation approach which provides estimates of exposure. All simulations will be performed on a secure server, freeing the user's computer for other tasks and limiting unauthorized access to the MCNP code. Technical challenges include creating a fully interactive 3D user interface, automating formation of a complex MCNP input file based on simple user inputs, handling multiple simultaneous users, maintaining server integrity, and reduction of intensive simulation computation time. [unreadable] [unreadable]